Radio-frequency transmitter and amplifier
View Patent ↗A method is provided for reducing non-linear effects in an electronic circuit including an amplifier. The method may include receiving a modulated signal at an input of the amplifier, the modulated signal comprising a baseband signal modulated by an oscillator frequency. The method may further include substantially attenuating counter-intermodulation in the modulated signal caused by harmonics of the oscillator frequency and the baseband signal by a resonant circuit. In some embodiments, the resonant circuit may include at least one inductive element and one capacitive element coupled to the at least one inductive element, the at least one inductive element and the at least one capacitive element configured to substantially attenuate counter-intermodulation in the modulated signal.
1. A radio transmitter, comprising:
an amplifier configured to:
receive a modulated signal at an amplifier input;
amplify the modulated signal; and
substantially reduce harmonics associated with at least one of an oscillator frequency and a baseband signal associated with the modulated signal.
2. A radio transmitter according to claim 1 , further comprising:
a modulator having an output coupled to the amplifier input, the modulator configured to modulate the baseband signal at the oscillator frequency to produce the modulated signal.
3. A radio transmitter according to claim 1 , wherein the amplifier comprises:
a transistor having at least three terminals; and
a resonant degeneration impedance coupled to a first terminal of the at least three terminals, the resonant degeneration impedance having at least one inductive element and at least one capacitive element coupled to the at least one inductive element.
4. A radio transmitter according to claim 3 , wherein the resonant degeneration impedance has at least one resonant frequency based on the at least one inductive element and the at least one capacitive element.
5. A radio transmitter according to claim 4 , wherein the resonant degeneration impedance is configured to substantially reduce a gain of the amplifier at the at least one resonant frequency of the resonant degeneration impedance.
6. A radio transmitter according to claim 4 , wherein the at least one resonant frequency is approximately equal to at least one harmonic frequency associated with at least one of the oscillator frequency and the baseband signal.
7. A radio transmitter according to claim 4 , wherein the at least one resonant frequency is approximately equal to one of three times the oscillator frequency and five times the oscillator frequency.
8. A radio transmitter according to claim 4 , wherein the resonant degeneration impedance is configured to have a first resonant frequency approximately equal to a first multiple of the oscillator frequency and a second resonant frequency approximately equal to a second multiple of the oscillator frequency.
9. An amplifier, comprising:
a transistor having at least three terminals; and
a resonant degeneration impedance coupled to a first terminal of the at least three terminals, the resonant degeneration impedance having at least one inductive element and at least one capacitive element coupled to the at least one inductive element.
10. An amplifier in accordance with claim 9 , wherein the resonant degeneration impedance has at least one resonant frequency based on the at least one inductive element and the at least one capacitive element.
11. An amplifier in accordance with claim 10 , wherein the resonant degeneration impedance is configured to substantially reduce the gain of the amplifier at the at least one resonant frequency of the resonant degeneration impedance.
12. An amplifier according to claim 9 , wherein the at least one inductive element and the at least one capacitive element are configured in parallel.
13. An amplifier according to claim 9 , wherein the resonant degeneration impedance is coupled between the first terminal and a signal ground of the amplifier.
14. An amplifier according to claim 9 , wherein the transistor comprises a bipolar junction transistor, and the resonant degeneration impedance is coupled to an emitter terminal of the bipolar junction transistor.
15. An amplifier according to claim 9 , wherein the transistor comprises a field-effect transistor, and the resonant degeneration impedance is coupled to a source terminal of the field-effect transistor.
16. A method for reducing non-linear effects in an electronic circuit including an amplifier, comprising:
receiving a modulated signal at an input of an amplifier having a resonant degeneration impedance, the modulated signal based on a baseband signal modulated by an oscillator frequency; and
amplifying the modulated signal and substantially reducing harmonics associated with at least one of the oscillator frequency and the baseband signal.
17. A method according to claim 16 , wherein substantially reducing harmonics comprises substantially reducing harmonics occurring at a frequency approximately equal to a multiple of the oscillator frequency.
18. A method according to claim 17 , wherein the resonant degeneration impedance comprises at least one inductive element and at least one capacitive element coupled to the at least one inductive element, the at least one inductive element and the at least one capacitive element having a resonant frequency approximately equal to the multiple of the oscillator frequency.
19. A method according to claim 16 , wherein substantially reducing harmonics comprises substantially reducing harmonics occurring at a frequency approximately equal to one of: three times the oscillator frequency and five times the oscillator frequency.
20. A method according to claim 19 , wherein the resonant degeneration impedance comprises at least one inductive element and at least one capacitive element coupled to the at least one inductive element, the at least one inductive element and the at least one capacitive element having a resonant frequency approximately equal to one of: three times the oscillator frequency and five times the oscillator frequency.